This invention relates to a selectively variable flowrate expansion apparatus or device for use on a refrigeration system for permitting the adiabatic expansion of a liquified refrigerant prior to the refrigerant entering an evaporator.
Generally, in a refrigeration system, it is necessary for liquified refrigerant (e.g., Freon or the like to undergo an adiabatic expansion process prior to the refrigerant entering the evaporator of the refrigeration system for removing heat from the environs of the evaporator. Typically, the expansion device may, in its simplest form, be constituted by a metering orifice or a capillary tube installed in the refrigerant line leading to the evaporator. The high pressure liquified refrigerant is forced or metered through the opening of the orifice or through the bore of the capillary tube, and permitted to adiabatically expand as it passes therethrough (or after it is passed through the orifice), such that the pressure on the liquid refrigerant is reduced within the evaporator, thus permitting the refrigerant to be readily vaporized in the evaporator. In other refrigeration systems, the expansion device comprises a so-called thermostatic expansion valve which has a spring biased valve member operable by a diaphragm actuator, the latter being responsive to evaporator temperatures by means of a capillary sensor bulb. Such an adjustable thermostatic expansion device is shown in U.S. Pat. No. 3,129,903. The valve of a thermostatic expansion valve is typically operable to permit increased or decreased refrigerant flow through the evaporator, dependent on the temperature of the refrigerant leaving the evaporator, which in turn is responsive to the heat load on the evaporator.
While thermostatic expansion valves are advantageous in that they regulate the flow of refrigerant through the evaporator so as to maintain a constant superheat, even though the system may experience different demands, thermostatic expansion valves are considerably more complicated and more expensive than simple orifices or capillary expansion devices. Capillary expansion devices, however, only permit a fixed flowrate of refrigerant therethrough, and thus the refrigeration system is not readily adjustable so as to vary the flowrate of refrigerant through the evaporator. In many prior orifice metering devices it was necessary to open up the refrigerant system to change orifices thereby resulting in a loss of refrigerant. Reference may be made to such U.S. Pat. Nos. 3,642,030 and 3,877,248 which illustrate prior art fixed orifice expansion devices.
In an effort to overcome the disadvantages of prior capillary or orifice expansion devices, variable or adjustable orifice or capillary tube expansion devices were developed. Such variable or adjustable expansion devices are shown in U.S. Pat. Nos. 4,184,342, 4,263,787, and 4,394,816. While these devices may have worked well for their intended purposes, they either were relatively of complicated construction and were difficult to adjust, or required a control system for automatic operation thereof.
Other prior art valves are known which may be material to the present invention. U.S. Pat. No. 1,017,292 discloses a steam valve having a cylindrical plug body which is rotatably received in a casing. A series of radial holes is provided in the plug body such that when one or more of the holes is in register with a radial neck, steam is free to flow through the valve. Importantly, the valve is not used in two-phase fluid service, as in an expansion device. Also, the size and spacing of holes in the plug body and the size of bore of the radial neck are such that more than one hole could be in register with the bore of the radial neck. This would make the steam valve difficult to use as a refrigerant expansion device.
U.S. Pat. No. 4,448,412 discloses an exercising apparatus which uses double acting hydrualic cylinders to act as a resistance exercise device. A rotatable, multiple position plug valve is used to meter the flow of hydraulic fluid into and out of the hydraulic cylinder thereby to change the resistance of the cylinder. However, this valve is not used as a refrigerant expansion device.
Lawrence, U.S. Pat. No. 2,701,704, discloses a valve which automatically cuts off the flow of fluid after a given quantity of fluid has passed through the valve. A valve plunger is slidably mounted with a cylindrical housing and is axially movable between an open position in which fluid may flow through the valve housing via a transverse bore in the valve plunger and a closed position in which flow is blocked. The valve plunger is spring-loaded toward its open position. Fluid from the inlet side of the valve is metered into a cylinder and piston arrangement via a pilot passage and an adjustable metering valve. When the cylinder is filled with fluid and is pressurized to a sufficient level, such as after there has been fluid flow through the valve for a predetermined length of time, the pressure forces on the valve plunger will overcome the spring and close the valve. However, this prior patent is not useful as a refrigerant expansion device.
Stamps et al, U.S. Pat. No. 3,326,232, discloses fertilizer application apparatus and has a rotary plug valve having a number of metering bores. However, this fertilizer application apparatus is not useful as a refrigerant expansion device.
None of these prior art references disclosed or suggested a refrigerant metering device having fixed capillary orifice bores which could be adjusted without opening the flow of refrigerant to vary the flow rate of a refrigerant and the superheat of a refrigeration system.